Many devices with displays use graphical user interfaces to display information to a user and to allow a user to interact with and control the device. Although computers commonly employ graphical user interfaces many other types of devices also may use graphical user interfaces. For example cell phones, household appliances, portable music and video players, consoles for sound studios, to name a few examples. Many of these types of devices include a graphical user interface element, often called a volume control, with which a user can control the volume of an audio signal or the loudness of sound generated by a device.
FIG. 1 shows an example of one type of volume control 100. A volume control may be situated in an audio signal path, which in FIG. 1 includes an upstream audio path 102 and a downstream audio path 104. Volume control 100 regulates an audio signal flowing between the upstream audio path 102 and the downstream audio path 104. A typical audio path in a computer may include: a microphone, a hardware switch; a sound card; a digital signal processor for noise filtering, amplification, etc.; an application with an acoustic echo cancellation and an automatic gain control; a mixer, possibly in software; an amplifier; and a medium for capturing a signal or speakers for producing sound. In FIG. 1 the upstream audio path 102 could be, for example, an application or a sound card or anything producing an audio signal. The downstream audio path 104 could be a mixer, an application for playing sound (e.g. a media player), etc. The upstream audio path 102 could be the input for a media player and the downstream audio path 104 could be anything receiving the media player's audio output. In simpler devices a volume control and its place in an audio path may be less distinct. The exact nature of the source and destination of an audio signal is not particularly important; a volume control can control any audio signal.
A volume control such as volume control 100 is usually a part of a larger graphical user interface or windowing system, which, for simplicity, is not shown in FIG. 1. As with many graphical user interfaces and elements, volume widget or volume control 100 has a part that the user sees and may interact with—volume control interface 106. Volume control 100 also has a control or logic part—volume control logic 108. The volume control logic 104 may be thought of as the “intelligence” of the volume control 100, and may maintain and manage state information, interaction rules, audio signal input and output, methods for the volume control 100, and so on. Typically, volume control logic 108 will maintain an audio level setting, for example in the form of a variable or property, which might control the volume or loudness of the audio signal being regulated by the volume control 100. The figure of volume control interface 106 is self-explanatory. A slider 110 may be interacted with to change the setting maintained by volume control logic 108. The slider 110 might be automatically moved by the volume control logic 108 to reflect changes in the audio level setting. A mute checkbox 112 may be checked and unchecked to mute and unmute the volume control 100. The volume control logic 108 may automatically move the slider 110 to reflect changes to the audio level setting. A numerical element 114 may present the audio level setting in textual form. The slider 110 or equivalent may serve the function of an audio level setting.
A user operates volume control 100 as follows. The user slides slider 110, perhaps by dragging a mouse, by clicking keys on a keyboard, by clicking keys on a keypad, by activating a software button, by pushing a hardware button, by rolling a hardware thumbwheel, by speaking a command, etc. In response slider 110 slides on a display, the audio level setting changes accordingly, and the volume or loudness of the audio signal is increased or decreased. Activation of the mute checkbox 112 will set the audio level setting to zero or some other pre-determined low-level setting.
Volume control 100 is only one example of a volume control. Volume controls can have a very wide range of appearances and behavioral attributes for controlling an audio level. Some other forms of volume controls are discussed herein but the exact form of a volume control is open-ended.
FIG. 2 shows various places in an audio system where a volume control may be used. Many computers have applications 120 that generate or receive audio data and feed audio signals into sound card channels 122 which in turn pass audio signals through (or are regulated by) a master volume control 124 which attenuates or amplifies a final mixed signal before it is sent to a power amplifier and loudspeaker(s). As seen in FIG. 2, volume controls may be used at any of these parts of the audio path.